#ifndef _HEAP_H
#define _HEAP_H

#include "Array.h"

template<class DATA, class KEY>
class Heap {

  struct Pair {
    DATA d;
    KEY k;
  };

  Array<Pair> heap;
  int n;

  int parent(int i) { return (i+1)/2 - 1; }
  int left_child(int i) { return 2*i + 1; };
  int right_child(int i) { return 2*i + 2; };

  void swap(int i, int j) {
    if (i == j) return;
    Pair tmp = heap[i];
    heap[i] = heap[j];
    heap[j] = tmp;
  }

public:
  Heap() : n(0) {};
  ~Heap() {};

  bool empty() { return n==0; }
  bool size() { return n; }
  
  void insert(DATA D, KEY K) {
    int i = n++;
    heap[i].d = D;
    heap[i].k = K;

    while (i != 0 && heap[i].k < heap[parent(i)].k) {
      swap(i, parent(i));
      i = parent(i);
    }
  }

  void delete_min(DATA&D, KEY& K) {
    if (empty()) die("Heap::delete_min called on empty heap");
    D = heap[0].d;
    K = heap[0].k;

    --n;
    swap(0, n);

    int i = 0;
    while (1) {
      int left = left_child(i);
      int right = right_child(i);
      int min = i;

      if (left < n && heap[left].k < heap[min].k) {
	min = left;
      }
      if (right < n && heap[right].k < heap[min].k) {
	min = right;
      }
      if (min == i) break;
      swap(i, min);
      i = min;
    }
  }

  void clear() {
    heap.clear();
    n = 0;
  }
};

#endif